In the solid drying technique, a convection electrical heating drying using hot air and a dehumidification cold air drying technique are known. For example, Patent Publication 1 discloses a food drying method to dry food by blasting food with cold air. According to this publication, food is placed on a transportation conveyor that is arranged to penetrate a drying room including therein an enclosed space and that has many ventholes in a conveyor face and the food is transported into the drying room. Then, dehumidification cool air is sent through nozzles provided at the upper and lower sides of the transportation conveyor to collide with the food. Then, a dehumidification cool air film is formed on the upper and lower surfaces of the food to thereby dry the food while transporting the food in the drying room. This can consequently improve the drying effect while maintaining the food flavor, thereby reducing the drying processing time and always forming a fixed temperature and humidity environment as a drying atmosphere around the food, which eliminates uneven drying.
Patent Publication 2 discloses, for example, a method and an apparatus to continuously dry rice and wet-field rice in particular. This publication has an objective of reducing the processing time and the grain core breakage by carrying out the preliminary cleaning of wet-field rice followed by the drying in a vortex layer to subsequently condition or cool the wet-field rice. Then, the rice is dried at a temperature of about 50 to 55° C. to include about 13% humidity. After being dried, the rice is gradually cooled/conditioned to have a surrounding temperature.
Patent Publication 3 discloses a cereal drying and storage method as well as a cereal drying and storage apparatus by which a single apparatus can provide both of the drying and storage while favorably maintaining the eating quality and quality of the rice.
According to this publication, the cereal drying and storage apparatus includes a heat pump unit. This unit has a ventilation flue including an upper path and a lower path formed by a branch wall. The upper path can be opened or closed by the first damper. The lower path can be opened or closed by the second damper. According to this configuration, when a drying operation is performed, the first damper can be closed and the second damper can be opened to thereby send normal temperature wind for dehumidification into a grain tank. When a storage operation is performed, the first damper can be opened and the second damper can be closed opened to thereby send cool wind for dehumidification into the grain tank. Thus, a single apparatus can provide both of the drying and storage operations.